1. Field of the Invention
The present invention relates to a useful and novel bifunctional filter membrane capable of simultaneous removal of metallic ions and nonionic materials from process water used in such applications as precision electronics industry, medical field, pharmaceutical industry and nuclear power generation.
2. Prior Art
Conventional methods of water treatment consist of first removing nonionic fine particles and microorganisms cells with micro filters or by cake filtration, then removing dissolved metallic ions with ion-exchange resins. These practices, however, involve complicated procedures and need a large volume of ion-exchange resins. Further, ion-exchange resins are fairly short-lived and present problems associated with the disposal of spent resins. Investigation has been undertaken to introduce ion-exchange groups into micro filter membranes but it has been difficult to completely solve the problems mentioned above on account of the drop in the ability to trap ions in the range of lower concentrations.